A lack of sleep has been linked to selfishness.
Researchers at the University of California found a bad night's sleep affects people's behaviour in social situations with tired people more likely to ignore the needs of others.
The findings were compiled by studying people's behaviour when they had a good night's sleep versus poor rest.
MRI scans of sleep-deprived people reveal less activation of empathy parts of brain.
Analysis of charitable donations in the US, spanning 15 years since 2001, saw a 10 percent drop in donations in states affected by following Daylight Saving Time. A similar decrease wasn't seen in states that do not change their clocks, or when states return to standard time in the fall.
The researchers hope their findings will allow people to reclaim a full night of sleep without embarrassment or the stigma of laziness.
A lack of sleep is also associated with increased risk of heart disease, poor mental health, depression, diabetes and high blood pressure.